Moveable barrier operators of various kinds are known in the art and include, for example, so-called garage door openers. Movable barrier operators typically serve to facilitate the automated movement of one or more corresponding movable barriers (such as, but not limited to, single panel and segmented garage doors, rolling shutters, pivoting and sliding gates, arm guards, and so forth). While the movable barrier operators are able to facilitate automated movement, it is often desirable to be able to manually operate the moveable barrier. To increase the flexibility of an automatic barrier operator, a manual override may be employed. For example, if there is a power loss or a malfunction of the operator, the user may want to manually move the garage door until such power loss or malfunction is remedied.
Garage door openers utilize various types of motor driven drive systems. Some drive systems use a motor driven chain which moves a “trolley” or arm which is connected to a barrier or door. The chain pulls the barrier or door open, or the motor which drives the chain, reverses and the chain pulls the barrier shut. For manual operation the trolley and chain are decoupled from the door.
Alternatively, rack and pinion or push-pull drive chain mechanisms are known to move the barriers between a closed and an opened position. In these latter mechanisms, the rack or the push-pull chain alternately push and pull a barrier between an open and closed position. U.S. Pat. No. 6,257,303 issued to Coubray describes a rack and pinion drive mechanism to open and close an overhead door where the rack and pinion drive mechanism moves the door on rollers up and down on parallel tracks near the edges of the door. In Coubray the pinion is not mounted on the tracks to position the pinion both before and after assembly of the system relative to a rack running along a channel inside the tracks. The drive pinion moves the door by engaging the rack within a rack channel that is associated with one of the tracks and the sectioned door. The Coubray rack and pinion mechanism is connected to the bottom of the door (see FIGS. 10A and 10B of U.S. Pat. No. 6,257,303 to Coubray) and the door is connected to the drive system through a clutch for connecting and disconnecting the motor via a keyed or dogged inter-engagement type of clutch. See Coubray at column 8, lines 1-5. For barrier operators that have internal limits, decoupling as described by Coubray results in the barrier operator losing positional information and not knowing where the barrier or door is with respect to the door limits of travel. This can result in the barrier operator slamming the barrier at a bottom or top physical limit which can cause damage to the barrier. Further, because Coubray's rack is coupled to the bottom of the door, this is not only inconvenient to the user, but potentially subjects the rack teeth to undue wear and the coupling mechanism to water, snow and other elements. This positioning also results in the Coubray pinion not being configured to exert driving forces upstream the pinion to drive the rack and door coupled to it upstream in the direction of the horizontal portion of the tracks and rack which are parallel to ground. Additionally Coubray does not describe the assembly of his system or how the parts of his system are configured to reduce installation error when the parts of the system are assembled on site. As a result of the forgoing, the Coubray system (1) may be prone to installation error because the engagement of the pinion with the rack is subject to misalignment during on site assembly or installation of the system which misalignment results in unnecessary wear, (2) looses its ability to properly stop at a set limit position when manually disconnected at the motor from the motor, and (3) is not versatile in not permitting coupling the rack to a barrier anywhere along the side of the barrier, especially when the barrier is an overhead moving door such as a garage door. In Coubray's system, the rack and pinion only pulls the door up and pushes it down due to the coupling of the rack to the door at the very bottom the door. Also in Coubray, when a user manually overrides the drive system, the motor is disconnected from the door at the motor and the user has to push or pull against the rack and pinion mechanism to move the door. This can cause the user considerable effort.
United States published patent application No. 2004/0177934 to Olmstead describes a garage door or barrier which is moved by a motor powered push-pull chain and a jack shaft. The jack shaft is mounted horizontally above the door opening with a sprocket at one end thereof and the end of the chain is connected to bottom of the door. In Olmstead manually moving the barrier causes the user to push or pull against the drive mechanism of the door. Indeed Olmstead expressly recognizes that “the push-pull chain 26 helps to keep individuals from raising the door” (paragraph 31, lines 15-16). This also makes it more difficult for the authorized user to manually move the garage door.
As mentioned, in the event of a power outage or system malfunction, a user may want to manually override the moveable barrier operator or drive mechanism to move the garage door. In standard barrier operators which use trolleys attached to a chain or belt, the moving chain may be disconnected from a trolley as described in U.S. Pat. No. 4,905,542 to Burm et al. With a trolley system as described in Burm, however, the motor usually is at an endpoint of an endless chain, and in such a system, fewer alternatives are available for positioning a motor which moves the barrier. This is not the case for a push pull mechanism, such as a rack and pinion drive.
Since a push-pull drive system, such as a rack an pinion drive or push-pull drive chain, may make manual operation of the garage door more difficult, it is advantageous to decouple the garage door from the drive system so that the user may manually move the door freely without having to work against the drive mechanism. Decoupling at the clutched arrangement which connects and disconnects the motor or barrier operator, as described in Coubray, disassociates the motor with the rack in such a way that the door may move independent of the motor. As described above, this may cause the motor to not retain the system limits which causes problems upon recoupling of the door to the motor. As mentioned, unregistered or unknown limits may result in the barrier operator slamming the barrier at the bottom or top physical limit which may cause damage to the barrier or drive system. Thus, reengagement of the connection between the door and the drive system in such a way as to retain the limits helps decrease unnecessary wear on the parts and assists in maintaining optimal performance of the system.
Positioning of the coupling mechanism along the tracks may also be important. The coupling mechanism may be positioned such that pinion or sprocket teeth may be pushing and pulling at different times during the opening and closing operations. For example, if the rack, pinion, and motor are near the top or bottom of the system, the wear on the system may be uneven. Further as described above, having the rack, pinion, and motor at the bottom of the door may deleteriously expose them to the elements such as rain, ice or snow. Some owners may desire the coupling mechanism be located at a specific location and thus it is desirable that the system be versatile such that the rack may be coupled to the barrier at a number of positions along the side of the barrier.